Design, synthesis, and evaluation of DNA topoisomerase II-targeted nucleosides

Microtubule associated proteins as targets for anticancer drug development

The dynamic equilibrium of tubulin-microtubule is an essential aspect of cell survivality. Modulation of this dynamics has become an important target for the cancer drug development. Tubulin exists in the alpha-beta dimer form which polymerizes to form microtubule and further depolymerizes back to tubulin dimer. The microtubule plays an essential role in mitosis and cell multiplication. Antitubulin drugs disturb the microtubule dynamics which is essentially required for DNA segregation and cell division during mitosis so killing the cancerous cells. Microtubule Associated Proteins (MAPs) interact with cellular cytoskeletal microtubules. MAPs bind to the either polymerized or depolymerized tubulin dimers within the cell and mostly causing stabilization of microtubules. Some of the tubulin binding drugs are in clinical use and others in clinical trial. MAPs inhibitors are also in clinical trial. Post-translational modification of lysine-40 either in histone or in alpha tubulin has an important role in gene expression and is balanced between histone deacetylases (HDACs) and histone acetyltransferases (HATs). HDAC inhibitors have the anticancer properties to form a drug for the treatment of cancer. They act by inducing cell cycle arrest and cell death. Some of the HDAC inhibitors are approved to be used as anticancer drug while others are under different phases of clinical trial. The present review updates on various MAPs, their role in cancer progression, MAPs inhibitors and their future prospects.

A Review of Progress in Histone Deacetylase 6 Inhibitors Research: Structural Specificity and Functional Diversity

Histone deacetylases (HDACs) are essential for maintaining homeostasis by catalyzing histone deacetylation. Aberrant expression of HDACs is associated with various human diseases. Although HDAC inhibitors are used as effective chemotherapeutic agents in clinical practice, their applications remain limited due to associated side effects induced by weak isoform selectivity. HDAC6 displays unique structure and cellular localization as well as diverse substrates and exhibits a wider range of biological functions than other isoforms. HDAC6 inhibitors have been effectively used to treat cancers, neurodegenerative diseases, and autoimmune disorders without exerting significant toxic effects. Progress has been made in defining the crystal structures of HDAC6 catalytic domains which has influenced the structure-based drug design of HDAC6 inhibitors. This review summarizes recent literature on HDAC6 inhibitors with particular reference to structural specificity and functional diversity. It may provide up-to-date guidance for the development of HDAC6 inhibitors and perspectives for optimization of therapeutic applications.

Photocatalytic Reductive Radical-Polar Crossover for a Base-Free Corey-Seebach Reaction

A metal-free generation of carbanion nucleophiles is of prime importance in organic synthesis. Herein we report a photocatalytic approach to the Corey-Seebach reaction. The presented method operates under mild redox-neutral and base-free conditions giving the desired product with high functional group tolerance. The reaction is enabled by the combination of photo- and hydrogen atom transfer (HAT) catalysis. This catalytic merger allows a C-H to carbanion activation by the abstraction of a hydrogen atom followed by radical reduction. The generated nucleophilic intermediate is then capable of adding to carbonyl electrophiles. The obtained dithiane can be easily converted to the valuable α-hydroxy carbonyl in a subsequent step. The proposed reaction mechanism is supported by emission quenching, radical-radical homocoupling and deuterium labeling studies as well as by calculated redox-potentials and bond strengths.

Dual inhibitors of histone deacetylases and other cancer-related targets: A pharmacological perspective

Epigenetic enzymes histone deacetylases (HDACs) are clinically validated anticancer drug targets which have been studied intensively in the past few decades. Although several drugs have been approved in this field, they are still limited to a subset of hematological malignancies (in particular T-cell lymphomas), with therapeutic potential not fully realized and the drug-resistance occurred after a certain period of use. To maximize the therapeutic potential of these classes of anticancer drugs, and to extend their application to solid tumors, numerous combination therapies containing an HDACi and an anticancer agent from other mechanisms are currently ongoing in clinical trials. Recently, dual targeting strategy comprising the HDACs component has emerged as an alternative approach for combination therapies. In this perspective, we intend to gather all HDACs-containing dual inhibitors related to cancer therapy published in literature since 2015, classify them into five categories based on targets' biological functions, and discuss the rationale why dual acting agents should work better than combinatorial therapies using two separate drugs. The article discusses the pharmacological aspects of these dual inhibitors, including in vitro biological activities, pharmacokinetic studies, in vivo efficacy studies, as well as available clinical trials. The review of the current status and advances should provide better analysis for future opportunities and challenges of this field.

The Antibacterial Activity and Mechanism of Action of Luteolin Against Trueperella pyogenes

Purpose

This research aimed to investigate the antibacterial activity and potential mechanism of luteolin against T. pyogenes.

Materials and Methods

The broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of luteolin against various T. pyogenes strains. The potential mechanism of action of luteolin was elucidated through testing and analysing the luteolin-induced alterations of T. pyogenes in several aspects, including cell wall, cell membrane, protein expression, nucleic acid content, topoisomerase activity and energy metabolism.

Results

The MIC values of luteolin against various T. pyogenes isolates and ATCC19411 were 78 µg/mL. The increased cell membrane permeability, destruction of cell wall integrity and TEM images after exposure to luteolin showed that the cell wall and membrane were damaged. The content of total protein and nucleic acid in T. pyogenes decreased significantly after treatment with luteolin (1/2 MIC) for 12, 24, and 36 h. Moreover, a hypochromic effect was observed in the absorption spectrum of luteolin when deoxyribonucleic acid (DNA) was added. In addition, after treatment with luteolin, a decrease in nicked or relaxed DNA content, which was catalysed by T. pyogenes-isolated DNA topoisomerase, was observed. In addition, the adenosine triphosphate (ATP) content in cells and the activity of succinate dehydrogenase (SDH) both decreased when T. pyogenes was exposed to different concentrations (1/4 MIC, 1/2 MIC, 1 MIC, 2 MIC) of luteolin for 1 h.

Conclusion

Luteolin showed distinct antibacterial activity against T. pyogenes by multiple actions, which mainly include destroying the integrity of the cell wall and cell membrane, influencing the expression of proteins, inhibiting nucleic acid synthesis, and interfering with energy metabolism.

Topoisomerase inhibitors: Pharmacology and emerging nanoscale delivery systems

Topoisomerase enzymes have shown unique roles in replication and transcription. These enzymes which were initially found in Escherichia coli have attracted considerable attention as target molecules for cancer therapy. Nowadays, there are several topoisomerase inhibitors in the market to treat or at least control the progression of cancer. However, significant toxicity, low solubility and poor pharmacokinetic properties have limited their wide application and these characteristics need to be improved. Nano-delivery systems have provided an opportunity to modify the intrinsic properties of molecules and also to transfer the toxic agent to the target tissues. These delivery systems leads to the re-introduction of existing molecules present in the market as novel therapeutic agents with different physicochemical and pharmacokinetic properties. This review focusses on a variety of nano-delivery vehicles used for the improvement of pharmacological properties of topoisomerase inhibitors and thus enabling their potential application as novel drugs in the market.

D-Ring-Modified Analogues of Luotonin A with Reduced Planarity: Design, Synthesis, and Evaluation of Their Topoisomerase Inhibition-Associated Cytotoxicity

A- and D-ring-modified luotonin-inspired heterocycles have been synthesized and were evaluated for their activity against the viability of four cancer cell lines in vitro, namely, MCF7, HCT116, JURKAT, and NCI-H460. The analysis of results indicated that two of the synthesized derivatives displayed good inhibition against the growth of the human colon cancer HCT116 cell line, with potencies lower than but in the same order of magnitude as camptothecin (CPT). These two luotonin analogues also showed an activity similar to that of the highly potent alkaloid CPT as inhibitors of topoisomerase I and also inhibited topoisomerase II. These results show that complete planarity is not a strict requirement for topoisomerase inhibition by luotonin-related compounds, paving the way to the design of analogues with improved solubility.

Novel Curcumin Inspired Antineoplastic 1-Sulfonyl-4-Piperidones: Design, Synthesis and Molecular Modeling Studies

Background:

Curcumin is a well-known example of plant origin exhibiting promising diverse biological properties such as, anti-inflammatory and antitumor as well as poor pharmacokinetic/pharmacodynamic properties. This is why effective agents based on its chemical scaffold were explored.

Methods:

A set of 3,5-bis(ylidene)-1-(alkylsulfonyl)piperidin-4-ones were synthesized in excellent yield (80- 96%) through dehydrohalogenation reaction of 3,5-bis(ylidene)-4-piperidinones with the corresponding alkane sulfonyl chloride in the presence of triethylamine. Antiproliferative properties of the synthesized compounds (dienone/curcumin inspired analogues) were studied by the standard MTT technique.

Results:

Most of the synthesized compounds revealed antiproliferative properties against HCT116 (colon) and A431 (skin/squamous) cancer cell lines with IC50 values at sub-micromolar level. Compound 36 also exhibited potency against MCF7 (breast) and A549 (lung) cancer cell lines (IC50 = 2.23, 4.27µM, respectively) higher than that of the reference standards (IC50 = 3.15, 5.93µM for 5-fluorouracil and doxorubicin against MCF7 and A549 cell lines, respectively). Cytotoxic properties of the synthesized compounds against non-cancer RPE1 cell line supported the safety profile of the effective agents against normal cells. Molecular modeling (3Dpharmacophore and 2D-QSAR) studies validated the observed bio-properties and explained the parameters governing activity. Inhibitory properties of compounds 27 and 29 (representative examples of the promising antiproliferative agents synthesized) supported their mode of action against topoisomerase IIα

Conclusion:

The synthesized scaffold is a promising antitumor agent (with special selectivity against colon and skin/squamous cancer cell lines) so, it can be considered for further investigation and development of highly effective hits/leads based on the computational models obtained.

Synthesis of carbazole derivatives containing chalcone analogs as non-intercalative topoisomerase II catalytic inhibitors and apoptosis inducers

Novel topoisomerase II (Topo II) inhibitors have gained considerable interest for the development of anticancer agents. In this study, a series of carbazole derivatives containing chalcone analogs (CDCAs) were synthesized and investigated for their Topo II inhibition and cytotoxic activities. The results from Topo II mediated DNA relaxation assay showed that CDCAs could significantly inhibit the activity of Topo II, and the structure-activity relationship indicated the halogen substituent in phenyl ring play an important role in the activity. Further mechanism studies revealed that CDCAs function as non-intercalative Topo II catalytic inhibitors. Moreover, some CDCAs showed micromolar cytotoxic activities. The most potent compound 3h exhibited notable growth inhibition against four human cancer cell lines. Flow cytometric analysis revealed that compounds 3d and 3h arrested the HL-60 cells in sub G1 phase by induction of apoptosis. It was further confirmed by Annexin-V-FITC binding assay. Western blot analysis revealed that compound 3h induces apoptosis likely through the activation of caspase proteins.